Butyrate prodrugs derived from lactic acid

ABSTRACT

This invention relates to butyrate prodrugs derived from lactic acid and pharmaceutical compositions and methods employing them, either alone or in combination with other agents, for increasing gamma globin and fetal hemoglobin in a patient. These compounds, compositions and methods are particularly effective in treating β-hemoglobinopathies, including sickle cell syndromes and β-thalassemia syndromes. In addition, this invention relates to the use of these prodrugs, alone or in combination with other agents, to stimulate cell differentiation which prevents proliferation of malignant cells. These methods are particularly useful in treating cancer, especially malignant hematological disorders.

TECHNICAL FIELD OF THE INVENTION

This invention relates to butyrate prodrugs derived from lactic acid andpharmaceutical compositions and methods employing them, either alone orin combination with other agents, for increasing gamma globin and fetalhemoglobin in a patient. These compounds, compositions and methods areparticularly effective in treating β-hemoglobinopathies, includingsickle cell syndromes and β-thalassemia syndromes. In addition, thisinvention relates to the use of these prodrugs, alone or in combinationwith other agents, to stimulate cell differentiation which preventsproliferation of malignant cells. These methods are particularly usefulin treating cancer, especially malignant hematological disorders.

BACKGROUND OF THE INVENTION

β-hemoglobinopathies are a group of inherited disorders of β-globinbiosynthesis. Although efforts have concentrated on a variety oftherapeutic regimens, feasible clinical treatments for thesedebilitating diseases remain scarce.

Various therapies have been utilized in the treatment ofβ-hemoglobinopathies, each accompanied by drawbacks. G. P. Rogers et.al., "Current and Future Strategies for the Management ofHemoglobinopathies and Thalassemia", Hematology 1994, Education ProgramAmerican Society of Hematology, pp. 9-20 (1994). Although thechemotherapeutic agent hydroxyurea stimulates fetal hemoglobinproduction and reduces sickling crisis in sickle cell anemia patients,its use in monotherapy is potentially limited by myelotoxicity and therisk of carcinogenesis. Potential long term carcinogenicity is also adrawback of 5-azacytidine-based therapies. Red blood cell transfusionsexpose patients to the potential of a wide range of infectious viralagents, as well as alloimmunization. Bone marrow transplants are not areadily available option for a large number of patients.Erythropoietin-based therapies have not proved consistent among a rangeof patient populations. Such varying drawbacks contraindicate the longterm use of such agents or therapies.

It is clear from multicenter studies involving numerous patients withsickle cell disease that increased blood levels of fetal hemoglobin areassociated with lower events of sickle cell crisis and longer survivaltime O. S. Platt et al., "Pain in Sickle Cell Disease, New Eng. J. Med.,325, pp. 11-16 (1991); O. S. Platt et al., "Mortality ion Sickle CellDisease", New Eng. J. Med., 330, pp. 1639-44 (1994)!. Accordingly, in aneffort to avoid the disadvantages of conventional therapies forβ-hemoglobinopathies, therapies have centered around ways to increasefetal hemoglobin production. Recent clinical trials have used butyrateanalogs, including arginine butyrate and isobutyramide, to stimulatefetal hemoglobin production as a means of treatment S. Perrine et al., AShort Term Trial of Butyrate to Stimulate Fetal-Globin-Gene Expressionin the β-globin Disorders", N. Eng. J. Med., 328, pp. 81-86 (1993); S.P. Perrine et. al., "Isobutyramide, an Orally Bioavailable ButyrateAnalogue, Simulates Fetal Globin Gene Expression In Vitro and In Vivo",British J. Haematology, 88, pp. 555-61 (1994); A. F. Collins et al.,"Oral Sodium Phenylbutyrate Therapy in Homozygous βThalassemia: AClinical Trial", Blood, 85, pp. 43-49 (1995).

Following the observation that butyric acid induces cell differentiationin vitro A. Leder and P. Leder, "Butyric Acid, a Potent Inducer ofErythroid Differentiation in Cultured Erythroleukemic Cells", Cell, 5,pp. 319-22 (1975)!, that compound was found to demonstrate promisingeffects in leukemia patients, by inducing cell differentiation A.Novogrodsky et al., "Effect of Polar Organic Compounds on LeukemicCells", Cancer, 51, pp. 9-14 (1983)!. Aside from their use in treatingβ-hemoglobinopathies, butyrate derivatives such as arginine butyrate, anarginine salt of butyric acid, have been shown to exert anti-tumor andanti-leukemia effects in mice C. Chany and I. Cerutti, "Antitumor EffectOf Arginine Butyrate in Conjunction with Corynebacterium Parvum andInterferon", Int. J. Cancer, 30, pp. 489-93 (1982); M. Otaka et al.,"Antibody-Mediated Targeting of Differentiation Inducers To Tumor Cells:Inhibition of Colonic Cancer Cell Growth in vitro and in vivo", Biochem.Biophys. Res. Commun., 158, pp. 202-08 (1989)!.

Although butyrate salts have the advantage of low toxicity as comparedwith conventional chemotherapeutic agents, their short half-lives invivo have been viewed as a potential obstacle in clinical settings A.Miller et al., "Clinical Pharmacology of Sodium Butyrate in Patientswith Acute Leukemia", Eur. J. Clin. Oncol., 23, pp. 1283-87 (1987);Novogrodsky et al., supra!. The rapid clearance of these agents resultsin an inability to deliver and maintain high plasma levels of butyratewhich necessitates administration by intravenous infusion. Anotherpotential obstacle to the use of butyrate salts is salt overload and itsphysiological sequelae.

In view of these observations, various prodrugs of butyric acid havebeen proposed for use in β-hemoglobinopathy and leukemia differentiationtherapies. Such prodrugs include tributyrin and n-butyric acid mono- andpolyesters derived from monosaccharides Z. Chen and T. Breitman,"Tributyrin: A Prodrug of Butyric Acid for Potential ClinicalApplication in Differentiation Therapy", Cancer Res., 54, pp. 3494-99(1994); H. Newmark et al., "Butyrate as a Differentiating Agent:Pharmacokinetics, Analogues and Current Status", Cancer Letts., 78, pp.1-5 (1994); P. Pouillart et al., "Pharmacokinetic Studies of N-ButyricAcid Mono- and Polyesters Derived From Monosaccharides", J. Pharm. Sci.,81, pp. 241-44 (1992)!. Such prodrugs have not proved useful astherapeutics, however, due to factors such as short half-life, lowbioavailability, low C_(max), or lack of effective oral deliverability.Other prodrugs, such as AN-9 and AN-10 A. Nudelman et al., "NovelAnticancer Prodrug of Butyric Acid", J. Med. Chem., 35, pp. 687-94(1992)!, elicit metabolites that may produce formaldehyde in vivo,leading to toxic effects in patients.

To date, conventional methods and therapeutic agents have not proved tobe safe and effective for all patients in the treatment ofβ-hemoglobinopathies. This is also the case for diseases characterizedby neoplastic, tumorigenic or malignant cell growth, or malignanthematological disorders. Accordingly, the need exists for alternativeshaving advantages over, and avoiding the disadvantages of, suchconventional methods and agents, while providing effective therapy forthose target diseases.

DISCLOSURE OF THE INVENTION

The present invention solves these problems by providing butyrateprodrugs of lactic acid and pharmaceutical compositions comprising them.These butyrate prodrugs demonstrate good bioavailability, effective oraldeliverability, good half-life and surprisingly high C_(max).

When administered to a patient, the butyrate prodrugs in thesecompositions release butyrate more efficiently than prior art butyrateprodrugs. This produces a higher plasma level of butyrate relative tothe amount of prodrug administered as compared to the prior art butyrateprodrugs.

Butyrate released from these prodrugs increase gamma globin synthesis,increase red blood cell hydration and stimulate cell differentiation.Increased gamma globin synthesis causes an increase in fetal hemoglobinformation which, in turn, increased the oxygen carrying capacity of redblood cells and prevents sickling. Increased hydration of red bloodcells also prevents sickling. The ultimate result of these cascades isthe increased survival of red blood cells.

This makes the pharmaceutical compositions of this inventionparticularly useful in methods for treating β-hemoglobinopathies,including sickle cell syndromes and β-thalassemia syndromes.

In addition, the ability of the butyrate prodrugs of this invention tostimulate cell differentiation has an anti-proliferative effect onmalignant cells, particularly malignant hemopoietic cells. Thus, thecompounds and pharmaceutical compositions of this invention may beemployed in methods for treating cancer, particularly malignanthematological disorders.

Because a patient can be treated with lower doses of the presentprodrugs in order to achieve a desired serum butyrate concentration,toxicity associated with the non-butyrate portion of the prodrug is lessof a concern.

All of these features facilitate the chronic therapy regimens oftenprescribed for patients suffering from β-hemoglobinopathies or cancer.At the same time, they also facilitate convenient dosing schemes for andpatient compliance with such therapy regimens. Furthermore, the methodsand compositions of this invention are not beset by the variety of sideeffects which typically characterize conventional therapy regimens.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts the time course of plasma butyric acid concentrationfollowing administration of the various doses of compound IIIc inindividual monkeys.

DETAILED DESCRIPTION OF THE INVENTION Definitions

The following definitions are used throughout the application.

As used herein, the term "alkyl", alone or in combination with any otherterm, refers to a straight-chain or branched-chain aliphatic hydrocarbonradical containing the specified number of carbon atoms, or where nonumber is specified, preferably from 1 to 10 carbon atoms, which maycontain one or more unsaturated bonds. Examples of alkyl radicalsinclude, but are not limited to, methyl, ethyl, isopropyl, butyl, pentyland the like. The term "alkyl", as used herein also includes the terms"alkenyl" and "alkynyl", which are defined below.

The term "alkenyl", alone or in combination, refers to a straight-chainor branched-chain alkenyl radical containing 2 to 10 and more preferablyfrom 2 to 6 carbon atoms. Examples of alkenyl radicals include, but arenot limited to, vinyl, allyl, E-propenyl, Z-propenyl, E,E-hexadienyl,E,Z-hexadienyl, Z,Z-hexadienyl and the like.

The term "alkynyl", alone or in combination, refers to a straight-chainor branched chain alkynyl radical containing from 2 to 10 and morepreferably from 2 to 6 carbon atoms. Examples of such radicals include,but are not limited to, ethynyl (acetylenyl), propynyl, propargyl,butynyl, 1,4-hexydiynyl, decynyl and the like. "Alkynyl", as usedherein, also refers to radicals containing both carbon-carbon doublebonds and carbon-carbon triple bonds, such as Z-pent-2-en-4ynyl.

The term "carbocyclyl", alone or in combination with any other term,refers to a carbocyclic radical, which may be saturated, partiallyunsaturated or aromatic, containing the specified number of carbonatoms, preferably from 3 to 14 carbon atoms and more preferably from 5to 10 carbon atoms. The term "carbocyclic" as defined include radicalsof "cycloalkyls", "cycloalkenyls" and carbocyclic "aryls". Carbocyclylalso refers to radicals containing several carbocyclic rings, which arefused or spiro-fused, comprising from 4 to 14 carbon atoms.

The term "cycloalkyl", alone or in combination, refers to a cyclic alkylradical containing from 3 to 8, preferably from 3 to 6, carbon atoms.Examples of such cycloalkyl radicals include, but are not limited to,cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl and the like.

The term "cycloalkenyl", alone or in combination, refers to a cyclicalkyl radical containing from 4 to 8, preferably from 5 to 6, carbonatoms and one or more double bonds. Examples of such cycloalkenylradicals include, but are not limited to, cyclopentenyl, cyclohexenyl,cyclopentadienyl and the like.

The term "heterocyclyl" refers to a carbocyclyl, preferably of 5 to 7atoms, containing from 1-4 heteroatoms independently selected fromoxygen, nitrogen and sulfur in place of an equal number of carbon atoms.That term also refers to substituted or unsubstituted, 8-11 memberedbicyclic ring systems, which may be aromatic or non-aromatic containingin either or both rings from 1-4 heteroatoms independently selected fromoxygen, nitrogen and sulfur and wherein the terms nitrogen and sulfurmay include any oxidized form of nitrogen and sulfur and thequarternized form of any basic nitrogen. A heterocyclyl group may beconnected to a structure through any atom of the group which results ina stable chemical bond.

Examples of non-aromatic heterocyclic radicals include, but are notlimited to, 2-pyrrolinyl, 3-pyrrolinyl, 1,3-dioxolyl, 2H-pyranyl,4H-pyranyl, piperidyl, 1,3-dioxanyl, 1,4-dioxanyl, morpholinyl,1,4-dithianyl, thiomorpholinyl, thiomorpholinyl sulfone,tetrahydrofuryl, piperazinyl and quinuclidinyl.

Examples of aromatic heterocyclic radicals include, but are not limitedto, 2-furyl, 3-furyl, 2-thienyl, 3-thienyl, 2-pyridyl, 3-pyridyl,4-pyridyl, pyrrolyl, oxazolyl, thiazolyl, imidazolyl, pyrazolyl,2-pyrazolinyl, pyrazolidinyl, isoxazolyl, isothiazolyl,1,2,3-oxadiazolyl, 1,2,3-triazolyl, 1,3,4-thiadiazolyl, pyridazinyl,pyrimidinyl, pyrazinyl, 1,3,5-triazinyl, 1,3,5-trithianyl, indolizinyl,indolyl, isoindolyl, 3H-indolyl, indolinyl, benzo b!furanyl, benzob!thiophenyl, 1H-indazolyl, benzimidazolyl, benzthiazolyl, purinyl,4H-quinolizinyl, quinolinyl, isoquinolinyl, cinnolinyl, phthalazinyl,quinazolinyl, quinoxalinyl, 1,8-naphthyridinyl, pteridinyl, carbazolyl,acridinyl, phenazinyl, phenothiazinyl, phenoxazinyl and the like.

The term "aryl" refers to an aromatic carbocyclic group, preferably of 6atoms, or an 8-14 membered aromatic polycyclic aromatic ring system;

Examples of "aryl" groups, include, but are not limited to, phenyl,1-naphthyl, 2-naphthyl, indenyl, azulenyl, fluorenyl and anthracenyl.

When substituted, each "carbocyclyl" and "heterocyclyl" mayindependently contain one to three substituents that are independentlyselected from hydroxy; halogen; C(1-6)-straight or branched alkyl,alkylamino or alkoxy; C(2-6)-straight or branched alkenyl, alkenylamino,alkynylamino, alkynyl, alkenoxy or alkynoxy; nitro, NH₂ ; thiol;alkylthio; carbocyclyl; carbocyclylalkyl; carbocyclylalkenyl;carbocyclylalkynyl; heterocyclyl; heterocyclylalkyl;heterocyclylalkenyl; heterocyclylalkynyl; methylenedioxy; carboxamido;alkylcarbonylamino; carbocyclylcarbonylamino; heterocyclylcarbonylamino;carbocyclylalkylcarbonylamino; heterocyclylalkylcarbonylamino;sulfonamido; alkylsulfonamido; alkenylsulfonamido; alkynylsulfonamido;and arylsulfonamido. The substituents listed above may be attached toeither a ring carbon atom or a ring heteroatom.

The term "alkoxy" refers to an O--C(1-6)-straight or branched alkylradical. Examples of alkoxy radicals include, but are not limited to,methoxy, ethoxy, n-propoxy, iso-propoxy, n-butoxy, isobutoxy, sec-butoxyand tert-butoxy.

The term "alkenoxy" refers to an O--C(2-6)-straight or branched alkenylradical. Examples of alkenoxy radicals include, but are not limited to,allyloxy, E and Z-3-methyl-2-propenoxy.

The term "alkynoxy" refers to an O--C(2-6)-straight or branched alkynylradical. Examples of alkenoxy radicals include, but are not limited to,propargyloxy and 2-butynyloxy.

The term "alkylamino" refers to a C(1-6)-straight or branched alkyl-NHradical or a C(1-6)-straight or branched alkyl-N--C(1-6)-straight orbranched alkyl radical where the alkyl radicals may be the same ordifferent. Examples of suitable alkylamino radicals include, but are notlimited to, methylamino, ethyl amino, propylamino, isopropyl amino,t-butyl amino, N,N-diethylamino and N,N-methylethylamino.

The term "alkenylamino" refers to a C(2-6)-straight or branchedalkenyl-NH radical, a C(2-6)-straight or branchedalkenyl-N--C(1-6)-straight or branched alkyl radical, or aC(2-6)-straight or branched alkenyl-N--C(2-6)-straight or branchedalkenyl radical where the alkenyl radicals may be the same or different.An example of a suitable alkenyl amino radical is, but is not limitedto, allylamino. Alkenylamino also refers to

The term "alkynylamino" refers to a C(3-6)-straight or branchedalkynyl-NH radical, a C(3-6)-straight or branchedalkynyl-NH--C(1-6)straight or branched alkyl radical, a C(3-6)-straightor branched alkynyl-NH--C(2-6)straight or branched alkenyl radical, or aC(3-6)-straight or branched alkynyl-N--C(3-6)-straight or branchedalkynyl radical where the alkynyl radicals may be the same or different.An example of a suitable alkynyl amino radical is, but is not limitedto, propargylamino and the like.

The term "amido" refers to a --C(O)NH₂ radical.

The term "alkylamido" refers to a --C(O)NH--C(1-6)-straight or branchedchain alkyl radical or a --C(O)N- C(1-6)₂ -straight or branched chainalkyl radical, wherein the two C(1-6)-straight or branched alkyl chainsmay be the same or different.

The term "alkylsulfonamido" refers to a C(1-6) straight or branchedchain alkyl-S(O)₂ NH-- radical. An example of alkylsulfonamido isethanesulfonamido.

In order that the invention herein described may be more fullyunderstood, the following detailed description is set forth.

The compounds of this invention are butyrate prodrugs derived fromlactic acid, which are represented by the Formula I: ##STR1##

wherein A and D are independently selected from the group consisting ofhydrogen, alkoxyalkyl, carbocyclylalkoxyalkyl or C(1-4)-straight orbranched alkyl, C(2-4)-straight or branched alkenyl or alkynyl, whichmay be independently substituted with hydroxy, alkoxy, carboxyalkyl,alkylamido, arylamido, heterocyclylamido, aralkylamido,heterocyclylalkylamido, alkoxycarbonylamino, alkenoxycarbonylamino,carbocyclyloxycarbonylamino, heterocyclyloxycarbonylamino,carbocyclylalkoxycarbonylamino, heterocyclylalkoxycarbonylamino,alkoxyalkoxycarbonylamino, amino, amido, carboxyl, thiol, thioalkyl,thiophenyl, aryl and heterocyclyl; provided that A and D are notsimultaneously hydrogen;

R is O, NH, NC(1-5)-straight or branched alkyl or NC(2-5)-straight orbranched alkenyl, any of which may be optionally substituted with acarbocyclyl or heterocyclyl moiety;

Z is hydrogen, C(1-4)-straight or branched alkyl, C(2-4)-straight orbranched alkenyl or alkynyl, carbocyclyl, or heterocyclyl, any of whichmay be optionally substituted with 1 or 2 groups independently chosenfrom C(1-3)-alkyl, C(2-3)-alkenyl or alkynyl, alkoxy, alkenoxy,alkynoxy, amido, thioalkyl, carbocyclyl or heterocyclyl; and

each stereogenic carbon may be in the R or S configuration;

provided that said compound is not ##STR2##

According to a preferred embodiment, D is methyl and A is hydrogen inthe compound of Formula I, yielding a compound of formula II: ##STR3##Preferably, in Formula II, R is O, NH, NC(1-3)-alkyl, NC(2-4)-straightor branched alkenyl or N-benzyl and Z is C(1-4)-straight or branchedalkyl optionally substituted with one group selected from a 5 to10-membered carbocyclyl or heterocyclyl. Most preferably, R is O, Z isan unsubstituted C(1-4)-straight or branched alkyl, and thestereochemistry at the methyl-bearing carbon is S.

According to another preferred embodiment, R is oxygen in Formula I,producing a compound of formula III: ##STR4## Preferably, in formulaIII, A and D are independently selected from hydrogen, methyl, ethyl orallyl; provided that A and D are not both hydrogen; and Z isC(1-3)-alkyl optionally substituted with one group selected fromC(5-10)-carbocyclyl or -heterocyclyl.

More preferably, D is hydrogen or methyl, A is unsubstitutedC(1-3)-alkyl and Z is unsubstituted C(1-3)-alkyl.

The more preferred pharmaceutical compositions of this inventioncomprise a compound selected from: ##STR5## The most preferred prodrugis compound IIIc.

The prodrugs of Formula I contain one or more asymmetric carbon atomsand thus occur as racemates and racemic mixtures, single enantiomers,diastereomeric mixtures and individual diastereomers. All such isomericforms of these compounds, as well as mixtures thereof, are included inthe pharmaceutical compositions of the present invention.

This invention also encompasses prodrugs of Formula I that arequarternized at any of the basic nitrogen-containing groups. The basicnitrogen can be quarternized with any agents known to those of skill inthe art including, for example, lower alkyl halides, such as methyl,ethyl, propyl and butyl chloride, bromides and iodides; dialkylsulfates, including dimethyl, diethyl, dibutyl and diamyl sulfates; longchain halides, such as decyl, lauryl, myristyl and stearyl chlorides,bromides and iodides; and aralkyl halides, including benzyl andphenethyl bromides. Water or oil-soluble or dispersible products may beobtained by such quarternization.

Prodrugs are hydrolyzed in vivo to release the active ingredient. In thecase of the present invention, the disclosed prodrugs release butyricacid. Without being bound by theory, we believe that a thresholdconcentration of butyric acid in the plasma is required to be maintainedfor a period of at least several hours during the day over a number ofdays to induce production of gamma globin chain synthesis and fetalhemoglobin formation, or to induce differentiation in malignant cells,leading to an anticancer effect. The compounds that characterize thecompositions of this invention are metabolized in the body in such a wayas to produce a high maximal concentration (C_(max)) of butyric acidfollowing oral administration. These compounds are also characterized bya sufficiently long half-life (t_(1/2)) that ensures good exposure ofthe patient to butyric acid. Due to the surprising and unexpectedly highC_(max), less of these prodrugs need to administered to produceeffective plasma concentration of butyric acid than conventional agents.This, in turn, results in lower potential for toxicity due to thecarrier portion of the prodrug, as well as easier administration.

The butyrate prodrugs of this invention may be synthesized by standardorganic routes. Many α-hydroxy acids, α-hydroxy esters and α-hydroxyamides are commercially available (e.g., Aldrich Catalog Handbook ofFine Chemicals, 1994-1995). In the case of α-hydroxy esters or α-hydroxyamides, derivatization of the hydroxy group may be carried out using anactivated form of butyric acid, such as an acid chloride; symmetricalacid anhydride; mixed carbonic, phosphonic, or sulfonic acid anhydrides;and activated esters such as phenyl, 4-nitrophenyl, pentafluorophenyl,hydroxybenzotriazolyl or N-hydroxysuccinimidyl.

Preferably the derivatization is carried out using a base suchtriethylamine, diisopropylethylamine, 1,8-diazabicyclo 54.0!undec-7-ene, pyridine or tetramethylguanidine; or aqueous buffers orbases such as sodium carbonate or sodium hydrogen carbonate (see, e.g.E. Haslam, "Recent Development in Methods for the Esterification andProtection of the Carboxyl Group", Tetrahedron, 36, pp. 2409-2433(1980). Dehydrating agents, such as 1,3-dicyclohexylcarbodiimide or1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride may also beemployed. The inclusion of a hyperacylation catalyst, such as4-dimethylaminopyridine, may improve the efficiency of the reaction (A.Hassner et al., "Direct Room Temperature Esterification of CarboxylicAcids", Tetrahedron Lett., 46, pp. 4475-4478 (1978)). Additional methodsare well known in the art and may be readily substituted for thoselisted above.

If α-hydroxy acids are used, derivatization of the carboxylic acid groupmay be carried out by first converting the hydroxy group to a butyrylgroup. This is followed by esterification or amidification of thecarboxylic acid, or alternatively by performing a sequence comprisingthe steps of:

1) transiently blocking the hydroxyl with a removable protecting group;

2) derivatizing the carboxylic acid as an ester or amide;

3) removing the hydroxyl protecting group; and

4) converting the hydroxy group to a butyryl group as above.

The butyrated or hydroxyl-protected α-hydroxy acids may then beconverted to their corresponding esters of Formula I (wherein R═O) bycarboxyl activation, similar to that described above for butyric acid,followed by reaction with an alcohol in the presence of a suitable base.Reaction of the activated butyrated or hydroxyl-protected α-hydroxyacids with primary or secondary amines yields amines of Formula I(wherein R═NH, N--C(1-5)-straight or branched chain alkyl, orN--C(2-5)-straight or branched chain alkenyl which may be substitutedwith a carbocyclyl or heterocyclyl moiety). A wide variety of primary,secondary and tertiary alcohols and primary and secondary amines arecommercially available or readily produced by methods known in the art.Therefore, this process provides access to compounds of Formula I whereR--Z may vary greatly.

Some particularly useful methods for synthesizing compounds of Formula Iare shown in Scheme I, below. ##STR6##

In these methods, the α-hydroxy acid of choice is simultaneously reactedat the hydroxyl and carboxylate groups. Reaction with a suitablesilylating reagent, for instance ^(t) butyl-dimethylsilyl chloride inthe presence of imidazole in dimethyl formamide, yields a bis-silylatedcompound of Formula XIa or similar silyl derivative. This compound canbe converted to a carboxyl-activated derivative by a sequencecomprising:

1) partial hydrolysis of carboxyl silyl group, for instance byhydrolysis using about 1 molar equivalent of lithium hydroxide at about-20° C. to about ambient temperature in aqueous dioxane; 2)concentration in vacuo;

3) careful acidification using for instance citric acid;

4) extraction into a suitable organic solvent such as methylenechloride; and

5) carboxyl activation as described above.

Removal of the hydroxyl-protecting silyl group using, for instance,tetrabutylammonium fluoride in tetrahydrofuran at about 0° C. to ambienttemperature, or HF-pyridine complex in acetonitrile, yields the hydroxyderivative XIV. Conversion to compounds of Formula I may then beeffectuated as described above.

Alternatively, the α-hydroxy acid of Formula X is simultaneously reactedat the hydroxyl and carboxylate groups with an alkyl substituent such asa benzyl derivative as shown in scheme I. Other alkyl derivatives suchas allyl, 4-methyloxybenzyl, 2,2,2-trichloroethyl or2-trimethylsilylethyl may also be used in this step.

The derivatization step may be accomplished by reaction of the compoundof Formula X with excess benzyl bromide in the presence of about 2.2-3equivalents of a strong base, such as sodium hydride, potassium hydride,or potassium ^(t) butoxide, in a suitable inert solvent, such as THF ordimethylformamide, at about -30° C. to about 100° C. depending on theparticular α-hydroxy acid and electrophile. Optionally, a phase-transfercatalytic method using a base such as K₂ CO₃ or NaOH in an inertsolvent, such as toluene or acetonitrile, may be used for thisalkylation. Suitable catalysts include quartenary ammonium salts, suchas ^(n) Bu₄ N⁺ Br⁻, and crown ethers, such as dibenzo-18-crown-6.

Conversion of suitably bis-alkylated compounds of Formula XIb to thoseof Formula XIIb may be accomplished by saponification, for instance inaqueous methanol or dioxane, using an equimolar or greater amount ofalkali metal base, such as hydroxides of sodium, lithium or potassium,at temperature ranging from about -40° C. to about 80° C. Alternatively,reaction with a thiolate anion, such as sodium ethyl thiolate,iodotrimethylsilane or with other ester-deprotecting reagents , willyield the protected carboxylic acid of Formula XIIb (see, e.g., R. C.Larock, "Comprehensive Organic Transformations", pp. 981-985, 1989 VCHPublishers, Inc., New York, N.Y.).

Activation and derivatization similar to that described for compounds ofFormula XIIa yield compounds of Formula XIIIb. The benzyl group may bethen conveniently removed, e.g., by catalytic hydrogenation using forinstance palladium or rhodium metal dispersed on carbon, using ahydrogen source such as hydrogen gas or ammonium formate, or catalytictransfer hydrogenation using cyclohexadiene or the like. Such methodsare well known in the art of organic chemistry (see, e.g., P. N.Rylander, "Catalytic Hydrogenation in Organic Synthesis", ©1979 AcademicPress, Inc., Orlando, Fla.). Reducing metal methods, involvingdissolving the substrate in liquid ammonia and adding an alkali metal,such as metallic sodium, are also known in the art.

If an allyl group is used in place of a benzyl group, its removal may beeffectuated by palladium transfer reactions using e.g.tetrakis(triphenylphosphine)Pd⁰ and an allyl acceptor, such asmorpholine or Pd^(II) acetate and Bu₃ SnH. Methods for employing theseand other alcohol protecting groups are described in the art (see, e.g.,T. W. Greene and P. G. M. Wuts "Protective Groups in Organic Synthesis",Second Edition ©1991 Academic Press, Inc., Orlando, Fla., pp. 14-120).The resulting compound of Formula XII may then be reacted as describedabove to produce compounds of Formula I.

α-Hydroxy acids, α-hydroxy esters and α-hydroxy amides, when notcommercially available, may conveniently be synthesized by a variety ofmethods which will be readily apparent to those of skill in the art. Forinstance, reaction of a glyoxylic acid ester or amide with a suitablecarbon-based nucleophile, such as a Grignard reagent, organocuprate oran organolithium reagent, in a suitable inert solvent, such as diethylether or tetrahydrofuran, at about -80° C. to about 0° C., will yield aα-hydroxy ester or amide of Formula XIV where A is the nucleophile and Dis hydrogen. Similar reactions, carried out on a-ketoesters or amides,yield α, α-disubstituted, α-hydroxyesters or amides (B. M. Trost and I.Fleming, "Comprehensive Organic Syntheses, Vol. I" pp. 49-282 ©1989,PerganLon Press, Oxford, England).

Many α-hydroxy acids may be produced conveniently by reacting thecorresponding α-amino acids with a diazetizing agent in a poorlynucleophilic medium. For example, NaNO₂ may be added to a solution of anamino acid in aqueous sulfuric acid (R. V. Hoffman et al., "Preparationof (r)-2-Azido Esters from 2-((p-Nitrobenzene)sulfonyl)oxy Esters andTheir Use as Protected Amino Acid Equivalents for the Synthesis of Di-and Tripeptides Containing D-Amino Acid Constituents", TetrahedronLett., 48, pp. 3007-3020 (1992)). Since numerous α-amino acids may bepurchased and many others can be made by known synthetic routes, oftenin optically active forms, (H. K. Chenault et al., "Kinetic Resolutionof Unnatural and Rarely Occurring Amino Acids: EnantioselectiveHydrolysis of N-Acyl Amino Acids Catalyzed by Acylase I", J. Am. Chem.Soc., 111, pp. 6354-6364 (1989)), this method provides a ready source ofstarting materials of formula I.

Alkyl carboxylic acids and their ester and amide derivatives may beconverted to α-hydroxy derivatives by formation of an anion at thecarbon α to the carboxylate derivative, followed by reaction with anoxygenating agent, such as N-sulfonyl oxaziradines, yield the compoundof Formula X or XIV (R. C. Larock, "Comprehensive OrganicTransformations", p. 489, ©1989 VCH Publishers, Inc., New York, N.Y.)

Variations of the methods disclosed above and other synthetic approachesknown in the literature of synthetic organic chemistry will be apparentto those of ordinary skill in the art. Alternate transient protectionand deprotection of reactive groups and their further transformation toproduce additional compounds of Formula I, will be readily apparent theskilled artisan.

According to one embodiment, the invention provides a pharmaceuticalcomposition comprising a prodrug of Formula I (including the n-butylester specifically excluded from the compounds of this invention) in anamount effective to increase the production of fetal hemoglobin orstimulate cell differentiation in a patient and a pharmaceuticallyacceptable carrier or adjuvant. More specifically, these compositionsare designed to treat a patient suffering from a β-hemoglobinopathy or amalignant disease. The term "malignant disease", as used herein denotesa condition characterized by neoplastic, tumorigenic or malignant cellgrowth, or a hematological disorder.

An amount effective to increase the production fetal hemoglobin orstimulate cell differentiation in a patient will depend, of course, onthe particular disease to be treated, the severity of the disease, thephysical condition of the patient and the judgment of the treatingphysician. Preferably, the prodrug of Formula I will be present in anamount capable of producing a plasma butyric acid concentration ofbetween about 0.03 mM and 3.0 mM within 8 hours of administration. Morepreferably, the prodrug of formula I is present in an amount thatproduces a plasma butyric acid concentration of between about 0.1 mM and1.0 mM within 6 hours of administration. Most preferably, the prodrug inthe composition is present in an amount that produces a plasma butyricacid concentration of between about 0.1 mM and 1.0 mM within 2 hours ofadministration and the concentration remains within that range for atleast 2 hours. Dosages of between about 25 mg prodrug/kg body weight and3 g prodrug/kg body weight administered one or more times per day arecapable of producing the desired plasma butyric acid concentration.Preferably, the patient will be administered the prodrug between 1 and 4times per day.

In a preferred embodiment, these compositions additionally comprise aconventional agent used in the treatment of β-hemoglobinopathies. Theconventional agent may be present in the same amount or less than thatnormally required to treat β-hemoglobinopathies in a monotherapy. Thenormal dosages of these conventional agents are well known in the art.Such agents include hydroxyurea, clotrimazole, isobutyramide,erythropoietin and salts of short-chain fatty acids, such asphenylacetic acid, phenylbutyric acid and valproic acid. Preferably, theconventional agent used is hydroxyurea.

According to an alternate preferred embodiment, the compositionscomprise a butyrate prodrug of this invention and a conventional agentused in the treatment of diseases characterized by neoplastic,tumorigenic or malignant cell growth, or a hematological disorder in apatient. This additional agent may be present in an amount equal to orless than that normally required to treat such diseases in amonotherapy. The normal dosages of these conventional agents are wellknown in the art. Such agents include, erythropoietin, or cancerchemotherapeutic agents, such as hydroxyurea or 5-azacytidine.Preferably, the conventional agent used is hydroxyurea.

Pharmaceutically acceptable salts of the prodrugs of Formula I(including the n-butyl ester specifically excluded from the compounds ofthis invention) may also be employed in any of the above-describedcompositions. Such salts may be derived from pharmaceutically acceptableinorganic and organic acids and bases.

Examples of suitable acids include hydrochloric, hydrobromic, sulfuric,nitric, perchloric, fumaric, maleic, phosphoric, glycollic, lactic,salicylic, succinic, toluene-p-sulfonic, tartaric, acetic, citric,methanesulfonic, ethanesulfonic, formic, benzoic, malonic,naphthalene-2-sulfonic and benzenesulfonic acids.

Salts derived from appropriate bases include alkali metal (e.g.,sodium), alkaline earth metal (e.g., magnesium), ammonium and N-(C₁₋₄alkyl)₄ ⁺ salts.

The carriers and adjuvants present in the compositions of this inventioninclude, for example, ion exchangers, alumina, aluminum stearate,lecithin, serum proteins, such as human serum albumin, buffersubstances, such as phosphates, glycine, sorbic acid, potassium sorbate,partial glyceride mixtures of saturated vegetable fatty acids, water,salts or electrolytes such as protamine sulfate, disodium hydrogenphosphate, sodium chloride, zinc salts, colloidal silica, magnesium,trisilicate, polyvinyl pyrrolidone, cellulose-based substances andpolyethylene glycol. Adjuvants for topical or gel base forms may beselected from the group consisting of sodium carboxymethylcellulose,polyacrylates, polyoxyethylene-polyoxypropylene-block polymers,polyethylene glycol and wood wax alcohols.

Generally, the pharmaceutical compositions of this invention may beformulated and administered to the patient using methods andcompositions similar to those employed for other pharmaceuticallyimportant agents. Any pharmaceutically acceptable dosage route,including, oral, topical, intranasal, or parenteral (includingintravenous, intramuscular, subcutaneous, intracutaneous, periosteally,intra-articular, intrasynovial, intrathecal, intrasternal, intracranialor intralesional) may be used.

The pharmaceutical compositions of this invention may be provided in avariety of conventional depot forms. These include, for example, solid,semi-solid and liquid dosage forms, such as tablets, pills, powdersliquid solutions, dilutions, suspensions, emulsions, liposomes,capsules, suppositories, injectable and infusible solutions. Thepreferred form depends upon the intended mode of administration andtherapeutic application.

For example, oral administration of the pharmaceutical compositions ofthis invention may be by any orally acceptable dosage form including,but not limited to, capsules, tablets, and aqueous or non-aqueoussuspensions, emulsions, oil dilutions and solutions. In the case oftablets for oral use, carriers which are commonly used include lactoseand corn starch. Lubricating agents, such as magnesium stearate, arealso typically added. For oral administration in a hard gelatin capsuleform, useful diluents include lactose and dried corn starch. Softgelatin capsules incorporating oils and/or polyethylene glycolsexcipients may also be used. When aqueous suspensions or emulsions areadministered orally, the prodrug is combined with emulsifying andsuspending agents. Flavoring, sweetening, or coloring agents may beadded, if desired.

Preferably, the pharmaceutical compositions of this invention areformulated for oral administration. Even more preferred are oralemulsions comprising between about 5 to 40% (w/w) of the prodrug ofFormula I (including the n-butyl ester specifically excluded from thecompounds of this invention) and an ionic or non-ionic surfactant withthe resulting composition having an HLB value of between 0-40. Preferredsurfactants include Tween-20, Tween-80, Spam-20, Spam-40 and poloxamers,such as S-108.

According to another embodiment, the invention provides methods fortreating a β-hemoglobinopathy in a patient. This method comprises thestep of treating the patient with any of the compositions describedabove. The term "treating", as used herein includes reducing theseverity, symptoms or effects of the β-hemoglobinopathy. Preferably, themethod provides a serum butyric acid concentration of between about 0.03mM and 3.0 mM within about 8 hours of administration. More preferably,this produces a plasma butyric acid concentration of between about 0.1mM and 1.0 mM within about 6 hours of administration. Most preferably,the prodrug in the composition is present in an amount that produces aplasma butyric acid concentration of between about 0.1 mM and 1.0 mMwithin 2 hours of administration and the concentration remains withinthat range for at least 2 hours. These plasma levels are achieved byadministering the prodrug of Formula I to the patient at a dose ofbetween about 25-3000 mg/kg body weight one or more times per day.Preferably, the patient will be administered the prodrug between 1 and 4times per day.

The β-hemoglobinopathies which may be treated by this method includesickle cell syndromes, such as sickle cell anemia, hemoglobin SCdisease, hemoglobin SS disease and sickle β-thalassemia; β-thalassemiasyndromes, such as β-thalassemia; other genetic mutations of theβ-globin gene locus that lead to unstable hemoglobins, such ascongenital Heinz body anemia, β-globin mutants with abnormal oxygenaffinity and structural mutants of β-globin that result in thalassemicphenotype. These diseases are described in The Molecular Basis of BloodDisease, vol. II, G. Stamatoyannopoulos et at., eds., pp. 157-244(1994).

According to a preferred embodiment, the above-described methodcomprises the additional step of treating the patient with an agent thatis normally used to treat such β-hemoglobinopathies, for e.g.,hydroxyurea. That agent may be administered prior to, sequentially withor after treatment with the butyrate prodrug-containing composition. Ofcourse, if the composition used to treat the disease is one that alreadycontains such conventional agent, this additional step can be omitted.

The amount of conventional agent administered in these methods ispreferably less than that normally required to treat such diseases in amonotherapy. The normal dosages of these conventional agents are wellknown in the art. Such agents include hydroxyurea, clotrimazole,isobutyramide, erythropoietin and salts of short-chain fatty acids, suchas phenylacetic acid, phenylbutyric acid and valproic acid. Preferably,the conventional agent used is hydroxyurea.

According to another embodiment, the invention provides method fortreating diseases characterized by neoplastic, tumorigenic or malignantcell growth, as well as malignant hematological disorders. Treatmentincludes prevention of the progression the disease or its recurrence.Such diseases include carcinomas, myelomas, melanomas, lymphomas andleukemias. Preferably, the method provides the same serum butyric acidconcentrations indicated above as being desirable for treatingβ-hemoglobinopathies.

According to a preferred embodiment, the above-described methodcomprises the additional step of treating the patient with an agent thatis normally used to such malignancies. Preferably, that agent ishydroxyurea. That agent may be administered prior to, sequentially withor after treatment with the butyrate prodrug-containing composition. Ofcourse, if the composition used to treat the disease is one that alreadycontains such conventional agent, this additional step can be omitted.

The amount of conventional agent administered in these methods ispreferably less than that normally required to treat such diseases in amonotherapy. The normal dosages of these conventional agents are wellknown in the art. Such agents include, erythropoietin, or cancerchemotherapeutic agents, such as hydroxyurea or 5-azacytidine.Hydroxyurea is a preferred conventional agent.

Combination therapies with conventional agents according to thisinvention (whether part of a single composition or administered separatefrom the prodrugs of this invention) may also exert an additive orsynergistic effect, particularly when each component acts to treat orprevent the target disease via a different mechanism.

In order that the invention described herein may be more fullyunderstood, the following examples are set forth. It should beunderstood that these examples are set forth for illustrative purposesonly and are not to be construed as limiting this invention in anymanner.

EXAMPLE 1 Synthesis of Compound IIIa and IIIb

We synthesized compound IIIa as follows. We combined 6.25 ml of methyl(S)-lactate with 13.75 ml of Et₃ N and then added that mixture to 50 mlof methylene chloride. We cooled this mixture to 0° C. in an ice bathand the slowly added 8.2 ml of butyryl chloride. This mixture wasstirred overnight and then filtered through a Buchner filter. Theprecipitate cake was then washed with ether and the wash was combinedwith the filtrate. The organic layer from the filtrate was isolated,washed twice with water, once with brine and then dried over anhydrousMgSO₄. The crude yield was 12.48 g.

The material was then dissolved in 90% hexane/ethyl acetate andchromatographed on an MPLC column. Fractions containing the desiredproduct were pooled and dried yielding 9.46 g of pure product. NMRanalysis confirmed that the pure product was compound IIIa.

Compound IIIb was synthesized and purified in an identical manner,substituting methyl (R)-lactate for methyl (S)-lactate.

EXAMPLE 2 Synthesis of Compound IIIc

We synthesized compound IIIc by combining 7.4 ml of ethyl (S)-lactatewith 13.75 ml of Et₃ N and then added that mixture to 50 ml of methylenechloride. We cooled this mixture to 0° C. in an ice bath and the slowlyadded 8.2 ml of butyryl chloride. This mixture was stirred overnight.TLC analysis of the mixture indicated incomplete reaction. We thereforeadded an additional 0.25 mole (2.5 ml) of butyryl chloride and allowedthe reaction to continue with stirring for 24 hours.

The mixture was then filtered through a Buchner filter. The precipitatecake was then washed with ether and the wash was combined with thefiltrate. The organic layer from the filtrate was isolated, washed twicewith water, once with brine and then dried over anhydrous MgSO₄. Thecrude yield was 15.98 g.

The material was then dissolved in 90% hexane/ethyl acetate andchromatographed on an MPLC column. Fractions containing the desiredproduct were pooled and dried yielding 9.97 g of pure product. NMRanalysis confirmed that the pure product was compound IIIc.

EXAMPLE 3 Oral Availability of Butyrate Prodrugs of Lactic Acid in Rats

We evaluated oral bioavailability and sustenance of plasmaconcentrations of butyric acid in rats receiving either compound IIIa,IIIb or IIIc by oral gavage at doses of approximately 3 g/kg bodyweight. The butyrate prodrugs were formulated by simple dilution in cornoil.

The assay was carried out according to the protocols described in Danielet al., Clinica Chimica Acta, 181, pp. 255-64 (1989); Planchon et al.,J. Pharm. Sci., 82, pp. 1046-48 (1993); Pouillart et al., J. Pharm.Sci., 81, pp. 241-44 (1992)!. Each compound was tested in five to sixrats (Sprague Dawley; Harlan Labs, Inc.) weighing approximately 300grams each. The relevant C_(max) for these agents are listed in Table 1,below.

                  TABLE 1    ______________________________________    Pharmokinetics of butyrate prodrugs of lactic acid in rats    Com-  Dose    No. of  Butyrate Butyrate                                           AUC    pound (g/kg)  Animals C.sub.max  (μM)                                   t.sub.max  (hr)                                           (mM/hr)    ______________________________________    IIIa  2.7     4        1335 ± 593.2                                   0.56 ± 0.31                                           2.10 ± 0.42    IIIb  2.5     6       147.0 ± 119.1                                   0.54 ± 0.49                                           0.26 ± 0.14    IIIc  3.0     6       456.3 ± 80.7                                   1.71 ± 1.3                                           1.68 ± 0.16    ______________________________________

These results demonstrate that the compounds of this invention are ableto release butyrate at a suitable rate and provide a sufficient plasmaconcentration of butyrate to be utilized in the treatment ofβ-hemoglobinopathies and cancer.

EXAMPLE 4 Oral Availability of Butyrate Prodrugs of Lactic Acid inMonkeys

Compound IIIc was further tested in anemic rhesus monkeys. A single oraldose of compound IIIc (0.3, 1.0 or 3.0 g/kg body weight) diluted in cornoil was administered to the monkeys. The C_(max) obtained at each ofthese doses is listed in Table II, below.

                  TABLE 2    ______________________________________    Pharmacokinetic parameters for Compound IIIc    in anemic rhesus monkeys            No. of   Butyrate    Butyrate                                         AUC    Dose (g/kg)            Animals  C.sub.max  (μM)                                 t.sub.max  (hr)                                         (mM/hr)    ______________________________________    0.3     2        214.4 ± 88.8                                 0.75    0.30 ± 0.03    1.0     2        509.9 ± 90.9                                 3.0     1.33 ± 0.09    3.0     2        836.1 ± 88.4                                 4.0     3.41 ± 0.03    ______________________________________

The time course of plasma butyric acid concentration followingadministration of the various doses of compound IIIc in individualmonkeys is depicted in FIG. 1.

EXAMPLE 5 Efficacy Studies of Compound IIIc/Hydroxyurea Combination InAnemic Rhesus Monkeys

The efficacy of compound IIIc administered in conjunction withhydroxyurea was tested on six anemic rhesus monkeys divided into threegroups of two each. Each group was studied in two phases, as shownbelow. Fetal hemoglobin cells (F cells), Hemoglobin F level in totalHemoglobin (% Hb F) and % γ globin chain levels were monitored beforeand after each of the two phases. % F cells were measured according tothe protocol described in Betke et al, Blut., 4, pp. 241-9 (1958). % HbF and % γ globin chain synthesis were measured using High PerformanceLiquid Chromatography (HPLC) according to the protocol described inHuisman, J. Chromagtogr., 418, pp. 277 (1987).

                  TABLE 1    ______________________________________    Phase I of the efficacy study           Number    Study  of                            Treatment    Group  Animals  Drug        Dose     Period    ______________________________________    I      2        Hydroxyurea 50 mg/kg/day                                         5 weeks    II     2        Compound IIIc                                1 g/kg/day                                         5 weeks    III    2        Compound IIIc                                3 g/kg/day                                         6 weeks    ______________________________________

                  TABLE 2    ______________________________________    Phase II of the efficacy study           Number    Study  of                            Treatment    Group  Animals  Drug        Dose     Period    ______________________________________    I      2        Hydroxyurea +                                50 mg/kg/day                                         5 weeks                    Compound IIIc    II     2        Compound IIIc                                1 g/kg/TID                                         5 weeks    III    2        Compound IIIc                                wash-out 4 weeks    ______________________________________

Animal 1 in group I had a % F cell count of 8-10% before Phase I. At theend of Phase I the % F cell count in Animal 1 increased to 25%. At theend of Phase II the % F cell count in Animal 1 increased to 35%. Animal2 in group II had a % F cell count of 8-10% before Phase I. At the endof Phase I the % F cell count in Animal 2 increased to 15%. At the endof Phase II the % F cell count in animal 2 increased to 22%. Theincrease in the % F cell count in Group I was accompanied by ameasurable increase in the % Hb F and % γ-globin chain levels. Groups IIand III showed a small but significant increase in % F cells with nomeasurable change in HbF or γ-globin chain levels.

In all three groups, there was no detectable difference in the levels ofthe triglycerides and ALT prior to or during the two phases of theefficacy study.

The results demonstrated the utility of the butyrates of the presentinvention, when used in conduction with conventional agents, such ashydroxyurea, for inducing fetal hemoglobin in β-hemoglobinopathies.

While we have hereinbefore described a number of embodiments of thisinvention, it is apparent that our basic constructions can be altered toprovide other embodiments which utilize the syntheses, processes andcompositions of this invention. Therefore, it will be appreciated thatthe scope of this invention is to be defined by the claims appendedhereto rather than by the specific embodiments which have been presentedhereinbefore by way of example.

We claim:
 1. A method for increasing fetal hemoglobin production in apatient comprising the step of administering to said patient apharmaceutical composition comprising:a. an amount of a butyrate prodrugof Formula I: ##STR7## effective to increase fetal hemoglobin; wherein:A and D are independently selected from the group consisting ofhydrogen, carbocyclylalkoxyalkyl or C(1-4)-straight or branched alkyl,C(2-4)-straight or branched alkenyl or alkynyl, which may beindependently substituted with hydroxy, alkoxy, carboxyalkyl,alkylamido, arylamido, heterocyclylamido, aralkylamido,heterocyclylalkylamido, alkoxycarbonylamino, alkenoxycarbonylamino,carbocyclyloxycarbonylamino, heterocyclyloxycarbonylamino,carbocyclylalkoxycarbonylamino, heterocyclylalkoxycarbonylamino,alkoxyalkoxycarbonylamino, amino, amido, carboxyl, thiol, thiomethyl,thiophenyl, aryl and heterocyclyl; provided that A and D are notsimultaneously hydrogen;R is O, NH, NC(1-5)-straight or branched alkylor NC(2-5)-straight or branched alkenyl, any of which may be optionallysubstituted with a carbocyclyl or heterocyclyl moiety; Z is hydrogen,C(1-4)-straight or branched alkyl, C(2-4)-straight or branched alkenylor alkynyl, carbocyclyl, or heterocyclyl, any of which may be optionallysubstituted with 1 or 2 groups independently chosen from C(1-3)-alkyl,C(2-3)-alkenyl or alkynyl, alkoxy, alkenoxy, alkynoxy, amido, thioalkyl,carbocyclyl or heterocyclyl; and each stereogenic carbon may be in the Ror S configuration; and b. a pharmaceutically acceptable adjuvant orcarrier.
 2. A method for stimulating cell differentiation in a patientcomprising the step of administering to said patient a pharmaceuticalcomposition comprising:a. an amount of a butyrate prodrug of Formula I:##STR8## effective to promote cell differentiation; wherein: A and D areindependently selected from the group consisting of hydrogen,carbocyclylalkoxyalkyl or C(1-4)-straight or branched alkyl,C(2-4)-straight or branched alkenyl or alkynyl, which may beindependently substituted with hydroxy, alkoxy, carboxyalkyl,alkylamido, arylamido, heterocyclylamido, aralkylamido,heterocyclylalkylamido, alkoxycarbonylamino, alkenoxycarbonylamino,carbocyclyloxycarbonylamino, heterocyclyloxycarbonylamino,carbocyclylalkoxycarbonylamino, heterocyclylalkoxycarbonylamino,alkoxyalkoxycarbonylamino, amino, amido, carboxyl, thiol, thiomethyl,thiophenyl, aryl and heterocyclyl; provided that A and D are notsimultaneously hydrogen;R is O, NH, NC(1-5)-straight or branched alkylor NC(2-5)-straight or branched alkenyl, any of which may be optionallysubstituted with a carbocyclyl or heterocyclyl moiety; Z is hydrogen,C(1-4)-straight or branched alkyl, C(2-4)-straight or branched alkenylor alkynyl, carbocyclyl, or heterocyclyl, any of which may be optionallysubstituted with 1 or 2 groups independently chosen from C(1-3)-alkyl,C(2-3)-alkenyl or alkynyl, alkoxy, alkenoxy, alkynoxy, amido, thioalkyl,carbocyclyl or heterocyclyl; and each stereogenic carbon may be in the Ror S configuration; and b. a pharmaceutically acceptable adjuvant orcarrier.
 3. The method according to claim 1, wherein said method is usedfor treating a β-hemoglobinopathy in said patient.
 4. The methodaccording to claim 3, comprising the additional step of administering tosaid patient a conventional agent for treating a β-hemoglobinopathy. 5.The method according to claim 3, comprising the additional step ofadministering to said patient hydroxyurea.
 6. The method according toclaim 2, wherein said method is used for treating a malignant disease insaid patient.
 7. The method according to claim 6, comprising theadditional step of adminstering to said patient a conventional agent fortreating a malignant disease.
 8. The method according to claim 6,comprising the additional step of adminstering to said patienthydroxyurea for treating a malignant disease in a patient.
 9. The methodaccording to claim 4 wherein said conventional agent is hydroxyurea. 10.The method according to claim 9, wherein the butyrate prodrug iscompound (IIIc). ##STR9##
 11. The method according to claim 7 whereinsaid conventional agent is hydroxyurea.
 12. The method according toclaim 11 wherein the butyrate prodrug is compound (IIIc).